In the conventional way, the fruits are harvested by straddling at least one row of plants with a harvesting unit mounted on the support structure of a harvesting machine that is moved along said row. To this end, the harvesting unit comprises a straddling chassis delimiting a harvesting tunnel into which the plants are introduced successively to move in said tunnel between a front opening and a rear opening of said tunnel.
To detach the harvest from the plants, the harvesting unit includes a shaker system comprising two shaker devices, said shaker devices being disposed on respective sides of the harvesting tunnel to delimit said tunnel transversely.
Moreover, the harvesting machine comprises a recovery system that makes it possible to convey the flow of harvest obtained in order to be able, possibly after cleaning and/or sorting it, to store it in at least one hopper provided for this purpose or in an attached trailer.
Each shaker device comprises at least one motorised member and advantageously a plurality of shaker members that are spaced vertically from one another, said members being intended to transmit by contact a shaking force to a plant introduced into the harvesting tunnel.
In the known manner, the shaker members have active parts that extend substantially horizontally in the longitudinal direction of the harvesting unit and are adapted to effect a sinusoidal to and fro movement in a horizontal and transverse direction perpendicular to the longitudinal direction of said unit in order for their active part to come periodically into contact with the plant.
In particular, as described in the document FR-2 605 487, each shaker member may comprise a rod that may have a small section compared to its length and be manufactured from a flexible material, for example one based on a polyester resin charged with glass fibres or based on a polyamide.
However, the use of such rods gives rise to a certain number of problems. In particular, when the shaker system is operating, in addition to the horizontal movements used to shake the plant, these rods effect parasitic movements, in particular in the vertical direction.
Now, these parasitic movements can cause detachment of leaves and/or branches from the plant which, in addition to causing damage harmful to the health of said plant, introduces into the flow of harvest waste that complicates subsequent cleaning of such harvest. Moreover, these parasitic movements increase the risk of collision between two consecutive members of a shaker device, which further reduces the efficacy of said members and increases the risk of breaking them.
Moreover, because of the repetitive impacts against the plants and/or possible individual impacts against the wood or concrete stakes that support said plants, the rods may become worn, notably at the level of their active part, which eventually leads to a reduction in their section and therefore to an increase in their flexibility.
Now, an increase in the flexibility of a rod reduces its efficacy in that, with a rod that is too flexible, it is more difficult to cause a plant to oscillate. Moreover, the more flexible a rod, the greater the risk of parasitic movements occurring. Because of this, it is necessary to replace the shaker rods after a certain time of use, which leads to disadvantages in terms of cost if said time of use is too short.
To alleviate these disadvantages there are known from the document FR-2 789 262 shaker members that feature a structure with at least one insert adapted to have the oscillatory characteristics required for said member, said insert being moreover covered by a jacket formed of a wear material different from the material from which said insert is made.
In particular, the wear jacket is made from a material and/or with dimensions, in particular in terms of thickness, that are chosen to make it possible for the oscillatory characteristics of the insert plus jacket combination, in other words the complete shaker member, to be virtually those of the insert alone. Wear of the jacket therefore has a minimum or even substantially no influence on the oscillatory characteristics and therefore on the efficacy of the shaker member, which makes it possible to increase its service life, which is advantageous.
However, this solution is not entirely satisfactory, in that the distribution of the insert in the jacket and/or the choice of the material for said insert do not make it possible to limit effectively the parasitic oscillations of the rods during use under difficult speed and/or climate conditions. In particular, these rods tends to resonate when the oscillation frequency is high, for example greater than 480 cycles per minute, and/or when the ambient temperature and/or relative humidity are high, which proves particularly disadvantageous for harvesting grapes.
The invention aims to improve on the prior art by proposing a shaker device the members of which are, thanks to a judicious choice of the material constituting the structural inserts, adapted to have increased efficacy, in particular at high oscillation frequencies, and over a wide range of wear.